tests: Rewrite the previous commit's sed_i helper

Last night's version looks unnecessarily ugly in the morning.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

tests/empdump-test

@@ -12,7 +12,7 @@ srcdir="$1"
 create_sandbox
 
 $files -f >/dev/null
-for i in `git ls-files "$testdir"/xundump-errors | uniq`
+for i in `perl "$srcdir"/src/scripts/ls-sources.pl "$testdir"/xundump-errors .`
 do run errors $empdump -ni "$i"
 done
 run errors $empdump -i "$testdir"/verify-prep

tests/test-common.sh

@@ -61,9 +61,11 @@ copy_tables()
 # sed -i isn't portable...
 sed_i()
 {
-    sed "$@" >sandbox/$$
-    shift $(($#-1))
-    mv sandbox/$$ "$1"
+    local script="$1"
+    shift
+    for i
+    do sed "$script" "$i" >sandbox/$$ && mv sandbox/$$ "$i"
+    done
 }
 
 customize()